“Whenever you feel like criticizing any one,” he told me, “just remember that all the people in this world haven’t had the advantages that you’ve had.”

From the start of the novel, Fitzgerald presents the theme of differences between social classes and races in 1920’s America by having his narrator say, wisely, that it is not fair to judge people by circumstances over which they have no control. It’s important that Nick’s family (which is not rich, but financially comfortable) taught him this belief, as it paints him as a correct and respectable man, and thus encourages us to view him as a trustworthy and honest narrator. Therefore, we can expect — to an extent — anything Nick says to be reasonable, including his criticism of people like Tom Buchanan, who love to criticize others precisely because they haven’t had the same advantages as he has.

But all narrators (even the narrator of an autobiographical work) have at least the potential to be unreliable narrators. Nick may be more judgmental throughout the novel than he realizes, even if his judgments are typically understated.